1. Field of Invention
The invention relates to umbrellas and more particularly to such an umbrella having a mechanism capable of opening the umbrella by pressing a push button with a main spring being expanded, closing the umbrella by pressing the push button again with stretcher springs being compressed, or after closing the umbrella compressing the main spring by urging a ferrule against, for example, the ground so that the umbrella can be opened again.
2. Description of Related Art
Conventionally, an umbrella can be classified as one having a telescopic shank and one without a telescopic shank. Also, umbrellas having automatic opening feature are commercially available. For umbrellas with telescopic shank having automatic opening feature, its folding sections are short and thus mechanism for effecting same is simple. To the contrast, for umbrellas without telescopic shank having automatic opening or closing feature, its folding sections are long and thus mechanism for effecting same is complicated. Such umbrella is disclosed in U.S. Pat. No. 5,141,010. However, so far as the inventor is aware, the devices shown in the prior art patents have had no market acceptance.
Typically, a main spring is provided in the shank so that a release of stored elastic energy by pressing a tab will open the umbrella. A plurality of stretcher springs are provided each between the stretcher and the rib so that pressing the stretcher springs will collapse the umbrella. That is, the opening is done by the elastic force of the main spring overcomes the resistance of the stretcher springs and the closing is done by the elastic force of the stretcher springs overcomes the resistance of the main spring which is, however, not feasible in terms of existing technology.
For overcoming the bottle neck, the inventor seeks a solution of making the main spring to be expansible in two steps in which in the first step the elastic force of the main spring is released to open the umbrella and in the second step the elastic force of the main spring is released as an complementary force of the elastic force of the stretcher springs so that the umbrella can be closed easily. Further, the release of the elastic force of the main spring is step by step in a control manner so as to be stable. Furthermore, the elastic force of the main spring is completely released in the umbrella closing step. Thus, a spring restoring step is required so that the main spring can be returned to a compressed state by storing elastic force for a future two-step expansion. This is the novel feature of the invention in the development of mechanism of automatically opening an umbrella without a telescopic shank. It is also known that umbrellas without a telescopic shank as widely used by people. Thus, continuing improvements in the exploitation of an umbrella without a telescopic shank having a novel automatic opening mechanism are constantly being sought.